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Abstract

The synthesis of gold nanoparticles (Au NPs) from HAuCl4 by using EDTA as a reducing agent is investigated for the first time using UV–vis spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). We show that the size of resulting Au NPs is dictated by the reactivity of ionic Au(III) species and the charge density of EDTA molecules with pH. Moreover by varying the pH of the reaction media, the size of Au NPs can be tuned from 25 to 100 nm. Investigation of the nucleation and growth of Au NPs by time-resolved UV–vis and TEM revealed the presence of nanowires that progressively increase in size at the same time the connected network is fragmented into small segments before the final spherical particles are formed. The identification of reaction intermediates and final products resulting from the reduction of Au(III) by EDTA was possible by recording several 1D- and 2D-nuclear magnetic resonance (NMR) spectra. Our results show that Au(III) reduction to Au(0) NPs by EDTA is accompanied by decarbonylation of EDTA and the formation of formaldehyde which, depending on pH, interferes with the reduction process and contributes to the synthesis. Besides the immense flexibility that can be provided by EDTA for further conjugation with functional molecules to diversify the surface functionality and in turn broaden the application, many synthetic routes concerned with the elaboration of nanoshells and core–shell metal nanoparticles use a large excess of the toxic formaldehyde as a reducing agent. Given the interest in biomedical applications of such nanomaterials and the important role of formaldehyde as a reducing agent in the synthesis process, using EDTA as a reducing agent can be a good starting point for minimizing or replacing formaldehyde use in the synthesis.

On the Synthesis of Au Nanoparticles Using EDTA as a Reducing Agent

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